This invention relates to a clutch combination especially adapted for use in the drive train of small horsepower power-driven implements, such as garden tractors, snowblowers, cultivators, mowers, and the like.
In such power-driven implements, it is in some cases necessary, and often desirable, to quickly disengage the drive train either to the propelling wheels of the implement or to the blade or other operating part of the implement. Coil spring clutches are advantageous for such disengagement, because they provide a quick declutching action with the use of a relatively simple and lightly loaded actuating device. Such clutches comprise, for example, a coil spring surrounding and frictionally engaged with aligned cylindrical clutch faces on coaxial driving and driven clutch members. The springg is wound of such a hand in relation to the forward driving direction of the clutch that the driving torque tends to wind the spring into tighter engagement with such clutch faces. The clutch is released by simply arresting the rotation of the leading end of the clutch spring, as by projecting a stop into the path of an out-turned tang on such leading end.
While such clutches are advantageous for their simple and inexpensive construction and their effective and quick release, they also have the serious disadvantage that re-engagement of the clutch is abrupt and harsh and imposes shock loads on the spring, so that such clutches cannot be used where they must be engaged under load.
The present invention provides a combination clutch which is of simple, compact, and inexpensive construction and provides a unitary assembly which may be embodied as such in the drive train of various implements. The combination provides all the advantages of the coil clutch, particularly its quick release with a simple actuator. It avoids the disadvantages of the coil clutch and provides a soft engagement which limits the torque load imposed on the coil spring as engagement occurs and which permits a variety of engagement characteristics. The assembly may also provide the speed-responsive engagement features commonly required in the propulsion drive train of a self-propelled vehicle, such as a self-propelled snowblower, garden tractor and the like. It may also be combined with a brake which may serve as a brake for the vehicle or may provide a safety control which, for example, stops the blade of a lawn mower or snowblower in response to release of a dead-man control. The coil spring clutch release mechanism may be actuated in common with, or in response to, the actuation of the brake. For other applications, especially low-speed applications, the combination may include a friction clutch which serves primarily to limit the torque transmitted through the drive train, both to protect the coil spring clutch from excessive loads as the clutch is engaged, and to protect the drive train from damage in the event the driven element strikes some obstruction.